glsnet(1) U.S. Geological Survey (wrdapp) glsnet(1) NAME glsnet - Regional hydrologic regression and network analysis using generalized least squares ABSTRACT The GLSNET procedure uses an analysis of residuals technique to estimate a regional regression equation to predict flow characteristics at ungaged sites. The regression analysis assigns different weights to observed flow characteristics. These weights are based on record length, cross correlation with flow characteristics at other sites, and an assumed model error structure. METHOD Stedinger and Tasker (1985, 1986) documented the usefulness of an estimated generalized least squares (EGLS) regression procedure for regional regression of streamflow characteristics. The EGLS procedure assigns different weights to observed flow characteristics based on their record length, cross correlation with flow characteristics at other sites, and the model error variance. Tasker and Stedinger (1989) provide further details on how the elements of the weighting matrix are determined. The problem of identifying the sites from which to collect future streamflow data is formulated as a mathematical program using regional information and is subject to budget constraints. An approximate solution is obtained using a step-backward technique that identifies gaging station sites, either existing or new, to discontinue data collection, or not start data collection, respectively, if the budget is exceeded. The method allows a network manager to design a nearly optimal streamflow data network for collecting regional information. HISTORY Version 2.6 1998/05/21 - Network analysis changed to run a zero planning horizon. Corrected a problem in the code that caused the program to quit if the user tried to have a 6th parameter in the network analysis regression equation. Version 2.5 1997/09/29 - Corrected an error in the calculation of the derivative of the objective function with respect to the number of years of record. Version 2.4 1997/05/09 - Changed how the average sampling error variance is computed in the network analysis. Should be faster. Simplified procedures for recompiling program with different dimensions. Version 2.3 1996/12/17 - Incorrect conversion of degree-minute- second latitudes and longitudes to decimal degrees (off by a factor of 10) has been corrected. This would have been a problem only in the following cases: 1. Latitudes and longitudes were stored in the WDM attributes 7 Jul 1998 1 glsnet(1) U.S. Geological Survey (wrdapp) glsnet(1) LATDMS & LNGDMS. (Note that data entered in the iowdm options peak, n-day, and (or) basin would not have this problem as lat/lng were stored as decimal degrees in attributes LATDEG & LNGDEG.) 2. When proposed stations were being added for the network analysis. Version 2.2 1995/10/08 - Increased the maximum number of stations from 300 to 600. 1995/10/21 - Fixed graphics to correctly handle Modify/Device. 1995/11/14 - Correction made in how peak qualification codes are being handled. There was a problem if the user specified no qualification codes (all peaks were to be included). In this case, peaks that had no qualification codes may not have been included. Version 2.1 1994/11/01 - Corrections made in the partial record option and the ordinary least squares option. Corrected a bug that caused the program to bomb when the user entered an invalid name for the input file. Corrected bugs that caused the ordinary least squares option to fail. DATA REQUIREMENTS At each site in the network of gages a set of basin characteristics, such as drainage area, basin slope, and mean annual precipitation; a set of flow characteristics, such as 100-year flood, mean annual flood, or 7-day 10-year low flow; and a time series of observed flows, such as annual peaks, or annual 7-day low flows; are required to be in a WDM file. OUTPUT OPTIONS Output is the final regression model and related residual analysis including influence statistics and various optional graphs. In addition, for the network analysis a list of stations to continue given various budget levels is output. SYSTEM REQUIREMENTS GLSNET is written in Fortran 77 with the following extension: use of include files. The ANN, WAIDE, AWSTAT, GRAPH, STATS, AIDE, WDM, ADWDM, and UTIL libraries from LIB are required to recompile. For more information, see System Requirements in LIB. DOCUMENTATION Tasker, G.D., and Stedinger, J.R., 1989, An operational GLS model for hydrologic regression: Journal of Hydrology, v. 111, p. 361-375. 7 Jul 1998 2 glsnet(1) U.S. Geological Survey (wrdapp) glsnet(1) REFERENCES Asquith, W.H., and Slade R.M, Jr., 1997, Regional Equations for estimation of peak-streamflow frequency for natural basins in Texas, U.S.Geological Survey Water-Resources Investigation Report 96-4307. Asquith, W.H., 1998, Peak-flow frequecny for tributaries of the Colorado River downstream of Austin, Texas, U.S.Geological Survey Water-Resources Investigation Report 98-4015. Brabets, T.P., 1996, Evaluation of the Streamflow-gaging network of Alaska in providing regional streamflow information, U.S.Geological Survey Water-Resources Investigation Report 96-4001. Clement, R.W., 1987, Floods in Kansas and techniques for estimating their magnitude and frequency: U.S. Geological Survey Water- Resources Investigations Report 87-4008. Curtis, G.W., 1987, Techniques for estimating flood-peak discharges and frequencies on rural streams in Illinois: U.S. Geological Survey Water-Resources Investigations Report 87-4207. Hodge, S.A, and Tasker, G.D., 1995, Magnitude and frequency of floods in Arkansas, U.S.Geological Survey Water-Resources Investigation Report 95-4224. Landers, M.N., and Wilson, K.V., Jr., 1991, Flood characteristics of Mississippi streams: U.S. Geological Survey Water-Resources Investigations Report 91-4037. Livingston, R.K., and Minges, D.R., 1987, Techniques for estimating regional flood characteristics of small rural watersheds in the Plains Region of eastern Colorado: U.S. Geological Survey Water- Resources Investigations Report 87-4094, 72 p. Ludwig, A.H., and Tasker, G.D., 1993, Regionalization of low flow characteristics of Arkansas streams: U.S. Geological Survey Water-Resources Investigations Report 93-4013, 19 p. Lui, S., and Stedinger, J.R., 1991, Low flow frequency analysis with ordinary and tobit regression: Proc. 18th annual conference and symposium ASCE WRPMD, p. 27-31. Lumia, R., 1991, Regionalization of flood discharges for rural, unregulated streams in New York: U.S. Geological Survey Water- Resources Investigations Report 90-4197. Medina, K.D., and Tasker, G.D., 1985, Analysis of surface water data network in Kansas for effectiveness in providing regional information: U.S. Geological Survey Water-Supply Paper 2203, 27 p. Roberts, J.W., and Kolton, G.F., 1989, Techniques for estimating 7 Jul 1998 3 glsnet(1) U.S. Geological Survey (wrdapp) glsnet(1) flood-peak discharges of rural, unregulated streams in Ohio: U.S. Geological Survey Water-Resources Investigations Report 89-4126. Stedinger, J.R., and Tasker, G.D., 1985, Regional hydrologic analysis 1: Water Resources Research, v. 21, no. 9, p. 1421-1432. Stedinger, J.R., and Tasker, G.D., 1986, Regional hydrologic analysis 2: Water Resources Research, v. 22, no. 10, p. 1487-1499. Tasker, G.D., 1986, Generating efficient gaging plans for regional information in Moss, M.E., ed., Integrated Design of Hydrological Networks: International Association of Hydrological Sciences publication no. 158, p. 269-281. Tasker, G.D., 1991, Identifying stream gauges to operate for regional information: Transportation Research Record 1319, p. 131-136. Vogel, R.M., and Kroll, C.N., 1990, Generalized low-flow frequency relationships for ungaged sites in Massachusetts: Water Resources Bulletin, v. 26, no. 2, p. 241-253. TRAINING Statistical Approach to Surface-Water Hydrologic Analysis (SW2011TC), offered annually at the USGS National Training Center. CONTACTS Operation and Distribution: U.S. Geological Survey Hydrologic Analysis Software Support Program 437 National Center Reston, VA 20192 h2osoft@usgs.gov Official versions of U.S. Geological Survey water-resources analysis software are available for electronic retrieval via the World Wide Web (WWW) at: http://water.usgs.gov/software/ and via anonymous File Transfer Protocol (FTP) from: water.usgs.gov (path: /pub/software). The WWW page and anonymous FTP directory from which the GLSNET software can be retrieved are, respectively: http://water.usgs.gov/software/glsnet.html --and-- /pub/software/surface_water/glsnet 7 Jul 1998 4 glsnet(1) U.S. Geological Survey (wrdapp) glsnet(1) SEE ALSO annie(1) - Program to list, table, plot data in a WDM file iowdm(1) - Program to store time-series data in a WDM file peakfq(1) - Flood-frequency analysis based on Bulletin 17B swstat(1) - Surface-water statistics wdm(1) - Watershed Data Management system 7 Jul 1998 5